This invention relates to a method of using titanium-doped aluminum oxide for passivation of ferroelectric materials and devices including the same and, more particularly, to a method of using titanium-doped aluminum oxide for passivation of ferroelectric materials and devices including the same in FeRAM and DRAM applications.
Ferroelectric random access memory (FeRAM) is a promising device because it has similar access and rewrite speeds as dynamic random access memory (DRAM), with the additional feature of non-volatility. The low power operation of FeRAMs is also a great advantage when used in Flash memory. FeRAM structures, therefore, may be widely used in the future, if these structures can be successfully integrated into real working devices.
The attempt to integrate ferroelectric materials into real devices, however, has resulted in many difficulties. In particular, when integrating the ferroelectric material into FeRAM and DRAM devices, the ferroelectric material is usually sandwiched between a bottom and a top electrode in order to polarize the ferroelectric material. Passivation of the ferroelectric material, therefore, usually requires passivation of the metal/ferroelectric/metal (MFM) structure. Platinum (Pt) has been widely used as the material for the top and bottom electrodes in ferroelectric material based devices such as capacitors. The major drawback of using Platinum as a top electrode is its catalytic nature with Hydrogen. It has been found that the integrity of the Platinum top electrode can be severely damaged during forming gas annealing (typically having a composition of approximately 95% nitrogen and 5% hydrogen) at 400 degrees Celsius for just thirty seconds. Furthermore, Platinum accelerates the decomposition of the H2 molecules into atomic Hydrogen which attacks and deoxidizes the oxide based ferroelectric material and degrades its ferroelectric properties. Accordingly, passivation layers have been deposited on the top Platinum electrode so as to shield the electrode and the ferroelectric material from the consequences of annealing in a forming gas ambient.
Titanium Dioxide (TiO2) has been shown to have passivation properties toward gas annealing in a forming gas ambient. For the forming gas annealing step, the pressure may range from only a few mTorr to 76 Torr or higher. A very thin layer of Al2O3 has also been shown to be effective in protecting ferroelectric capacitors during forming gas annealing. However, MFM structures with TiO2 passivation layers have been shown to be more susceptible to leakage after the forming gas annealing step. Al2O3 layers deposited by physical vapor deposition (PVD) show large stress factors and are difficult to oxidize. Some researchers have used Si3N4 as a passivation layer. However, it has been found that when a Si3N4 layer is deposited directly on the top electrode an undesirable reaction occurs between the Si3N4 and the top electrode.
Due to these deficiencies in the passivation layers heretofore utilized, which are susceptible to problems during the forming gas annealing step of manufacturing, prior art ferroelectric devices have a reduced remnant polarization and a reduced dielectric constant of the ferroelectrial material after annealing.
This invention comprises a passivation material that can be used in nonvolatile memory devices, DRAMs, capacitors, pyroelectric infrared sensors, optical displays, optical switches, piezoelectric transducers, and surface acoustic wave devices. More particularly, the invention comprises a titanium-doped aluminum oxide layer for passivation of ferroelectric materials and a method of manufacturing the same and, more particularly, to a titanium-doped aluminum oxide layer for passivation of ferroelectric materials that has reduced stress and improved passivation properties, and that is easy to deposit and be oxidized.
In one embodiment the invention comprises an integrated circuit device comprising a ferroelectric material positioned between first and second metal electrodes; and a passivation layer positioned on said first electrode, said passivation layer comprising Titanium doped Aluminum Oxide. The invention also comprises a method of manufacturing an integrated circuit device including a ferroelectric structure having a passivation layer, comprising the steps of: providing a deposition chamber; providing in said deposition chamber a ferroelectric structure including a ferroelectric material positioned between top and bottom electrodes; providing Aluminum and Titanium targets in said deposition chamber; and sputtering said Aluminum and said Titanium targets so as to form a Titanium doped Aluminum Oxide passivation layer on said top electrode.
Accordingly, an object of the invention is to provide a passivation material that can be used in nonvolatile memory devices, DRAMs, capacitors, pyroelectric infrared sensors, optical displays, optical switches, piezoelectric transducers, or surface acoustic wave devices.
Another object of the invention is to provide a titanium-doped aluminum oxide layer for passivation of ferroelectric materials and a method of manufacturing the same.
A further object of the invention is to provide a titanium-doped aluminum oxide layer for passivation of ferroelectric materials that has reduced stress and improved passivation properties
Still a further object of the invention is to provide a titanium-doped aluminum oxide layer for passivation of ferroelectric materials that is easy to deposit and be oxidized.